Reinforcing structure comprising spun staple yarns

ABSTRACT

This invention pertains to a tire, a transfer hose, a hydraulic hose, a conveyor belt or a power transmission belt comprising a structural fibrous reinforcing component, the component further comprising spun staple yarn having a linear density corresponding to a cotton count of from 17/1 to 10/5.

BACKGROUND

1. Field of the Invention

This invention pertains to a structural fibrous reinforcing component for use in a tire or elastomeric belt or hose.

2. Description of Related Art

Reduction in tire noise is an ongoing objective of the tire industry. Most tires include components incorporating continuous filament yarns to provide structural reinforcement. Spun staple yarns can provide a tire component having lower stiffness and higher dampening characteristics, both desirable features for lowering noise from a tire.

SUMMARY OF THE INVENTION

This invention pertains to a tire, a transfer hose, a hydraulic hose, a conveyor belt or a power transmission belt comprising a structural fibrous reinforcing component, the component further comprising spun staple yarn having a linear density corresponding to a cotton count of from 17/1 to 10/5.

DETAILED DESCRIPTION

By spun staple fiber is meant a fiber produced on a cotton, woolen, worsted or similar spinning machine from a feedstock of cut filaments or yarn (staple), the cut filaments or yarns being typically from about 10 mm to 300 mm in length. In some applications, the cut filaments or yarns have a cut length that is from about 10 mm to 150 mm. The spun staple fibers are normally bound together in the yarn by a twist. Preferred spinning techniques are ring spinning, rotor spinning, air-jet spinning or friction spinning. Such spun staple yarns and the processes for making them are well known in the textile industry.

For purposes herein, the term “filament” is defined as a relatively flexible, macroscopically homogeneous body having a high ratio of length to width across its cross-sectional area perpendicular to its length. The filament cross section can be any shape, but is typically circular or bean shaped. Herein, the term “fiber” is used interchangeably with the term “filament”. A plurality of filaments are combined to form a multifilament yarn.

In some embodiments, the spun staple yarn has a linear density corresponding to a cotton count of from 17/1 to 10/5. In some other embodiments the yarn has a linear density corresponding to a cotton count of from 10/2 to 10/4. In some embodiments, the staple spun yarn comprises the same fibers.

In some embodiments, the spun staple yarn is in the form of a singles yarn comprising a blend of fibers. A singles yarn is a term well understood in the textile art.

In some other embodiments, the spun staple yarn is a blend of yarns that are twisted together to form a merged yarn. The individual yarns comprising the merged yarn may themselves be twisted.

In yet some other embodiments, the spun staple yarn is a sheath-core yarn comprising at least one continuous filament in the core and spun staple yarn in the sheath. The continuous filament of the core may be either polymeric, inorganic, natural fiber or metallic. Suitable polymers for the continuous filaments are aromatic polyamide, aromatic copolyamide, aliphatic polyamide, polyester, rayon, modacrylic, polyolefin, acrylic, polyazole, liquid crystal polymer, or polylactic acid (PLA). Suitable inorganic fibers include carbon or glass. Natural fibers include those based on cellulose. A preferred metallic filament or strand is steel.

Spun Staple Yarn Composition

The same materials described here may also be used as the continuous filament component in the core of the sheath-core fiber previously described.

Suitable fibers for the spun staple yarn are aromatic polyamide, aromatic copolyamide, aliphatic polyamide, polyester, rayon, modacrylic, polyolefin, acrylic, polyazole, liquid crystal polymer, or polylactic acid. Suitable inorganic fibers include carbon or glass. A suitable natural fiber is a cellulose such as Lyocell or rayon. Some fibers may be in the form of nanotubes. Both single- wall and multi-wall nanotubes are suitable.

A preferred aromatic polyamide is para-aramid. The term “aramid” means a polyamide wherein at least 85% of the amide (—CONH—) linkages are attached directly to two aromatic rings. Suitable aramid fibers include Twaron®, Sulfron®, Technora® all available from Teijin Aramid, Heracon™ from Kolon Industries Inc. or Kevlar® available from E.I. du Pont de Nemours and Company, Wilmington Del. (DuPont). Aramid fibers are described in Man-Made Fibres—Science and Technology, Volume 2, Section titled Fibre-Forming Aromatic Polyamides, page 297, W. Black et al., Interscience Publishers, 1968. Aramid fibers and their production arealso disclosed in U.S. Pat. Nos. 3,767,756; 4,172,938; 3,869,429; 3,869,430; 3,819,587; 3,673,143; 3,354,127; and 3,094,511.

One preferred para-aramid is poly (p-phenylene terephthalamide) which is called PPD-T. By PPD-T is meant the homopolymer resulting from mole-for-mole polymerization of p-phenylene diamine and terephthaloyl chloride and also copolymers resulting from incorporation of small amounts of other diamines with the p-phenylene diamine and of small amounts of other diacid chlorides with the terephthaloyl chloride. As a general rule, other diamines and other diacid chlorides can be used in amounts up to as much as about 10 mole percent of the p-phenylene diamine or the terephthaloyl chloride, or perhaps slightly higher, provided only that the other diamines and diacid chlorides have no reactive groups which interfere with the polymerization reaction. PPD-T, also, means copolymers resulting from incorporation of other aromatic diamines and other aromatic diacid chlorides such as, for example, 2,6-naphthaloyl chloride or chloro- or dichloroterephthaloyl chloride or 3,4′-diaminodiphenylether.

Additives can be used with the aramid and it has been found that up to as much as 10 percent or more, by weight, of other polymeric material can be blended with the aramid. Copolymers can be used having as much as 10 percent or more of other diamine substituted for the diamine of the aramid or as much as 10 percent or more of other diacid chloride substituted for the diacid chloride or the aramid.

Another suitable fiber is one based on aromatic copolyamide which may be prepared by reaction of terephthaloyl chloride (TPA) with a 50/50 mole ratio of p-phenylene diamine (PPD) and 3,4′-diaminodiphenyl ether (DPE). Yet another suitable fiber is that formed by polycondensation reaction of two diamines, p-phenylene diamine and 5-amino-2-(p-aminophenyl) benzimidazole with terephthalic acid or anhydrides or acid chloride derivatives of these monomers.

An example of aliphatic polyamide is nylon. Suitable types of nylon include nylon 6; nylon 6,6; nylon 6,10; nylon 6,12; nylon 11 and nylon 12.

When the polymer is polyolefin, in some embodiments, polyethylene or polypropylene is preferred. Polyolefin fibers can only be used when the processing temperatures required to compound the fiber and elastomerin order to calender or extrude the compound or to cure the compound in the tire assembly is less than the melting point of the polyolefin. The term “polyethylene” means a predominantly linear polyethylene material of preferably more than one million molecular weight that may contain minor amounts of chain branching or comonomers not exceeding 5 modifying units per 100 main chain carbon atoms, and that may also contain admixed therewith not more than about 50 weight percent of one or more polymeric additives such as alkene-1-polymers, in particular low density polyethylene, propylene, and the like, or low molecular weight additives such as anti-oxidants, lubricants, ultra-violet screening agents, colorants and the like which are commonly incorporated. Such is commonly known as extended chain polyethylene (ECPE) or ultra high molecular weight polyethylene (UHMWPE). Preparation of polyethylene fibers is discussed in U.S. Pat. Nos. 4,478,083, 4,228,118, 4,276,348 and 4,344,908. High molecular weight linear polyolefin fibers are commercially available. Preparation of polyolefin fibers is discussed in U.S. Pat. No. 4,457,985.

Examples of polyazoles are polyarenazoles such as polybenzazoles and polypyridazoles. Suitable polyazoles include homopolymers and also copolymers. Additives can be used with the polyazoles and up to as much as 10 percent, by weight, of other polymeric material can be blended with the polyazoles. Also, copolymers can be used having as much as 10 percent or more of other monomer substituted for a monomer of the polyazoles. Suitable polyazole homopolymers and copolymers can be made by known procedures, such as those described in or derived from U.S. Pat. Nos. 4,533,693, 4,703,103, 5,089,591, 4,772,678, 4,847,350, and 5,276,128.

Preferred polybenzazoles include polybenzimidazoles, polybenzothiazoles, and polybenzoxazoles and more preferably such polymers that can form fibers having yarn tenacities of 30 grams per denier (gpd) or greater. In some embodiments, if the polybenzazole is a polybenzothioazole, preferably it is poly (p-phenylene benzobisthiazole). In some embodiments, if the polybenzazole is a polybenzoxazole, preferably it is poly (p-phenylene benzobisoxazole) and more preferably the poly (p-phenylene-2,6-benzobisoxazole) called PBO.

Preferred polypyridazoles include polypyridimidazoles, polypyridothiazoles, and polypyridoxazoles and more preferably such polymers that can form fibers having yarn tenacities of 30 gpd or greater. In some embodiments, the preferred polypyridazole is a polypyridobisazole. One preferred poly(pyridobisozazole) is poly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole which is called PIPD. Suitable polypyridazoles, including polypyridobisazoles, can be made by known procedures, such as those described in U.S. Pat. No. 5,674,969.

The term “polyester” as used herein is intended to embrace polymers wherein at least 85% of the recurring units are condensation products of dicarboxylic acids and dihydroxy alcohols with linkages created by formation of ester units. This includes aromatic, aliphatic, saturated, and unsaturated di-acids and di-alcohols. The term “polyester” as used herein also includes copolymers (such as block, graft, random and alternating copolymers), blends, and modifications thereof. In some embodiments, the preferred polyesters include poly (ethylene terephthalate), poly (ethylene naphthalate), and liquid crystalline polyesters. Poly (ethylene terephthalate) (PET) can include a variety of comonomers, including diethylene glycol, cyclohexanedimethanol, poly(ethy1ene glycol), glutaric acid, azelaic acid, sebacic acid, isophthalic acid, and the like. In addition to these comonomers, branching agents like trimesic acid, pyromellitic acid, trimethylolpropane and trimethyloloethane, and pentaerythritol may be used. The poly (ethylene terephthalate) can be obtained by known polymerization techniques from either terephthalic acid or its lower alkyl esters (e.g. dimethyl terephthalate) and ethylene glycol or blends or mixtures of these. Another potentially useful polyester is poly (ethylene napthalate) (PEN). PEN can be obtained by known polymerization techniques from 2,6 napthalene dicarboxylic acid and ethylene glycol.

Liquid crystalline polyesters may also be used in the invention. By “liquid crystalline polyester” (LCP) herein is meant polyester that is anisotropic when tested using the TOT test or any reasonable variation thereof, as described in U.S. Pat. No. 4,118,372. One preferred form of liquid crystalline polyesters is “all aromatic”; that is, all of the groups in the polymer main chain are aromatic (except for the linking groups such as ester groups), but side groups which are not aromatic may be present. A suitable material is available under the tradename Vectran from Kuraray Company Ltd.

Polylactic acid or polylactide (PLA) is a thermoplastic aliphatic polyester derived from renewable resources, such as corn starch, tapioca products (roots, chips or starch) or sugar canes.

Acrylic fibers are synthetic fibers made from polyacrylonitrile and have an average molecular weight of about 100,000, about 1900 monomer units. In some embodiments, the polymer contains at least 85% acrylonitrile monomer. Typical comonomers are vinyl acetate or methyl acrylate.

Modacrylic fiber is a synthetic copolymer fiber made from acrylonitrile and other polymers. Such fibers can be obtained from Solutia Inc. or Kaneca Corporation.

E-Glass is a commercially available low alkali glass. One typical composition consists of 54 weight % SiO₂, 14 weight % Al₂O₃, 22 weight % CaO/MgO, 10 weight % B₂O₃ and less then 2 weight % Na₂O/K₂O.

Some other materials may also be present at impurity levels.

S-Glass is a commercially available magnesia-alumina-silicate glass. This composition is stiffer, stronger, more expensive than E-glass and is commonly used in polymer matrix composites.

Carbon fibers are commercially available and well known to those skilled in the art. In some embodiments, these fibers are about 0.005 to 0.010 mm in diameter and composed mainly of carbon atoms.

Cellulosic fibers can be made by spinning liquid crystalline solutions of cellulose esters (formate and acetate) with subsequent saponification to yield regenerated cellulosic fibers. Another suitable natural fiber is a cellulose such as Lyocell, a cellulose from wood pulp, or rayon.

Staple yarns can also be produced from metallic slivers such as steel.

Fabric

In some embodiments, the structural fibrous reinforcing composite component is a fabric containing spun staple yarn.

One example of a fabric is a woven fabric. The term “woven” is meant herein to be any fabric that can be made by weaving; that is, by interlacing or interweaving at least two filaments or yarns typically at right angles to each other. Generally such fabrics are made by interlacing one set of filaments or yarns called warp yarns, with another set of filaments or yarns, called weft or fill yarns. The woven fabric can have essentially any weave, such as, plain weave, crowfoot weave, basket weave, satin weave, twill weave, unbalanced weaves, and the like.

In some other embodiments, the fabric comprises filaments or yarns that are aligned parallel to each other. This type of fabric is frequently referred to as a unidirectional fabric. In some instances a unidirectional fabric may contain a few filaments or yarns oriented in a different orientation to the unidirectionally aligned yarns solely for the purpose of providing some stability to the unidirectional fabric and prevent the fabric from falling apart. Such filaments or yarns normally constitute less than five percent or even less than three percent of the total filaments or yarns of the fabric.

Another type of suitable fabric is a knit fabric. A knit fabric is formed by interlocking a series of loops of one or more yarns.

Adhesion Coating

Preferably, the fabric comprising the spun staple yarn is coated with a surface coating for promoting adhesion to rubber. In some embodiments the coating comprises from 0.1 to 25 or from 1 to 20 or even from 2 to 15 weight percent of the yarn plus coating. It is preferable that the coating penetrates at least three filaments deep into the fabric. Preferably, the amount of coating applied should be the minimum necessary to promote good adhesion of rubber to the fabric as an excessive amount of coating can increase the stiffness of the fabric.

Generally, the coating is the same as can be used as for dipped tire cords. The coating can be selected from epoxies, isocyanates and various resorcinol-formaldehyde latex (RFL) mixtures. In some embodiments, the coating material is an epoxy resin subcoat and a resorcinol-formaldehyde topcoat. Such coatings are well known in the tire and mechanical rubber goods trade.

Elastomeric Article

The fabric comprising spun staple yarns, preferably coated with an adhesion promoting agent, can be used as a structural component in a tire and in mechanical rubber goods like a transfer hose, a hydraulic hose, a conveyor belt or a power transmission belt.

Suitable components in a tire that can comprise the fabric include a carcass, sidewall, belt, overlay, breaker, chipper, flipper or subtread. An overlay is a preferred component.

Production of Tires

In some aspects, the invention concerns processes for producing a tire comprising fibrous cords where the process comprises, as one step, producing one or more layers by calendering or extruding elastomeric sheet. The process can additionally comprise consolidating a plurality of layers of elastomer.

One process involves high shear mixing of raw materials (elastomer and other additives) to compound the elastomer followed by roll milling and/or calendering. The high shear mixing ensures that the ingredients are uniformly dispersed in the elastomer. The first compounding process phase involves mastication or breaking down of the polymer. Natural rubber may be broken down on open roll mills, but it is a more common practice to use a high shear mixer having counter rotating blades such as a Banbury or Shaw mixer. Sometimes, a separate premastication step may be used. For synthetic rubbers, premastication is only necessary when the compound contains a polymer blend. This is followed by masterbatching when most of the ingredients are incorporated into the rubber. This ensures a thorough and uniform ingredient dispersion in the rubber. During the mixing process, it is important to keep the temperature as low as possible. Ingredients not included in this step are those constituting the curing system. These are normally added in the last step, usually at a lower temperature.

Further information on elastomer compounding is contained in pages 496 to 507 of The Vanderbilt Rubber Handbook, Thirteenth Edition, published by R. T. Vanderbilt Company Inc., Norwalk, Conn., and in U.S. Pat. Nos. 5,331,053; 5,391,623; 5,480,941 and 5,830,395.

In some circumstances, mixing of ingredients can also be achieved by roll milling. A calender is a set of multiple large diameter rolls that squeezes rubber compound into a thin sheet.

Another approach is to use an extrusion process where the raw materials are mixed and extruded into a sheet in a single process. The extruder consists of a screw and barrel, screw drive, heaters and a die. The extruder applies heat and pressure to the compound. For tire treads, the die cross sectional profile is adapted to the desired tread design and the tread can be extruded in one piece.

There are three main stages in tire production, namely component assembly, pressing, and curing. In component assembly, a drum or cylinder is used as a tool onto which the various components are laid. During assembly, the various components are either spliced or bonded with adhesive. A typical sequence for layup of tire components is to first position a rubber sheet inner liner. Such a liner is compounded with additives that result in low air permeability. This makes it possible to seal air in the tire. The second component is a layer of calendered body ply fabric or cord coated with rubber and an adhesion promoter. The body ply or plies are turned down at the drum. Steel beads are applied and the liner ply is turned up thereby wrapping the bead. Bead rubber includes additives to maximize strength and toughness. Next, the apex is positioned. The apex is a triangular extruded profile that mates against the bead and provides a cushion between the rigid bead and the flexible inner liner and body ply assembly. This is followed by a pair of chafer strips and the sidewalls. These resist chafing when mounting the tire onto the rim. The drum is then collapsed and the first stage assembly is ready for the second component assembly stage.

Second stage assembly is done on an inflatable bladder mounted on steel rings. The green first stage assembly is fitted over the rings and the bladder inflates it up to a belt guide assembly. Steel belts to provide puncture resistance are then placed in position. The belts are calendered sheets consisting of a layer of rubber, a layer of closely spaced steel cords and a second rubber layer. The steel cords are oriented radially in a radial tire construction and at opposing angles in a bias tire construction. Passenger vehicle tires are usually made with two or three belts. An overlay is applied over the top belt. Examples of these techniques can be found in U.S. Pat. No. 6,106,752 (injection molding); U.S. Pat. No. 6,899,782 (extrusion) and U.S. Pat. No. 7,005,022 (extrusion and needling).

The final component, the tread rubber profile of subtread and tread block layers, is then applied. The tread assembly is rolled to consolidate it to the belts and the finished assembly (green cover) is then detached from the machine. Many higher-performance tires include an optional extruded cushion component between the belt package and the tread to isolate the tread from mechanical wear from the steel belts. If desired, the tire building process can be automated with each component applied separately along a number of assembly points. Following layup, the assembly is pressed to consolidate all the components into a form very close to the final tire dimension.

Curing or vulcanizing of the elastomer into the final tire shape takes place in a hot mold. The mold is engraved with the tire tread pattern. The green tire assembly is placed onto the lower mold bead seat, a rubber bladder is inserted into the green tire and the mold closed while the bladder inflates to a pressure of about 25 kgf/cm². This causes the green tire to flow into the mold, thereby taking on the tread pattern. The bladder is filled with a recirculating heat transfer medium such as steam, hot water or inert gas. Cure temperature and curing time will vary for different tire types and elastomer formulations but typical values are about 150 to 180 degrees centigrade with a curing time from about 12 to 25 minutes. For large tires, the cure time can be much longer. At the end of the cure, the pressure is bled down, the mold opened and the tire stripped from the mold. The tire may be placed on a post-cure inflator that will hold the tire fully inflated while it cools.

Test Method

The invention is illustrated by the following examples that are designed to be illustrative but not limiting in nature, wherein all parts, proportions, and percentages are by weight unless otherwise indicated.

EXAMPLES

In the following examples, identical test specimens, both in composition and dimensions, were used to represent the overlay and treadband composition and structure. Typically, the treadband area includes all tire components including carcass plies, belts, overlay and tread but excludes sidewall, apex, and bead components. In the construction of a conventional tire different compositions may be used for this component part.

The length of the staple yarn prior to spinning was about 2.5 inches (63.5 mm). The staple yarn used to make the cabled yarn of Example 1 had a linear density of 2.5 denier per filament (DPF). A rubber compound similar to that described above was used in all examples. The rubber was formed into a sheet via milling and calendaring. Prior to incorporation with the rubber, all cords were dipped in a resorcinol-formaldehyde-latex dispersion, a process well known in the mechanical rubber goods industry.

Comparative Example A

In this example, rubber sheets comprising continuous filament cords of nylon 6,6 at 32 ends per inch (approximately 13 ends per cm) were incorporated into a compounded rubber strip. The strip was placed over a cylindrical molded rubber composite that mimics a tire with inner-liner, carcass and belt components in place. The components were assembled on a mandrel and the rubber cured under heat and pressure to give a cured rubber cylinder representative of a tire. The overlay and belt cords wrapped around the cylinder and thus were orthogonal to the main axis of the cylinder and carcass cords were parallel to the main axis of the cylinder.

Example 1

In Example 1, cords of spun staple para-aramid yarn replaced the continuous filament cords of comparative Example A. The spun-yarn para-aramid cords were made by cabling two ends of 10/1 cc 100% para-aramid yarn at a balanced twist of 2.4 twist multiplier. The cords were then dipped into RFL solution at conditions optimized for the spun yarn for improved adhesion to rubber. The cords were then incorporated into the rubber as per Comparative Example A. The rubber composition was the same as for Comparative Example A. The strip of compounded rubber comprising the spun staple para-aramid yarn was molded as per Comparative Example A.

Testing of the above samples to simulate noise emitted from a tire would demonstrate a significant noise reduction from the design of Example 1 when compared with that of Comparative Example A. 

We claim:
 1. A tire, a transfer hose, a hydraulic hose, a conveyor belt or a power transmission belt comprising a structural fibrous reinforcing component, the component further comprising spun staple yarn having a linear density corresponding to a cotton count of from 17/1 to 10/5.
 2. The component of claim 1, wherein the yarn is penetrated by a surface coating for promoting adhesion to rubber such that the coating comprises from 0.1 to 25 weight percent of the yarn plus coating.
 3. The component of claim 1, wherein the spun staple yarn has a linear density corresponding to a cotton count of from 10/2 to 10/4.
 4. The component of claim 1, wherein the yarn is a singles yarn comprising a blend of fibers.
 5. The component of claim 1, wherein the yarn is a blend of yarns that are twisted together to form a merged yarn.
 6. The component of claim 1, wherein the yarn is a sheath-core yarn comprising at least one continuous filament in the core and spun staple yarn in the sheath.
 7. The component of claim 1, wherein the spun staple yarn is aromatic polyamide, aromatic copolyamide, aliphatic polyamide, polyester, rayon, carbon, glass, modacrylic, polyolefin, acrylic, polyazole, liquid crystal polymer, cellulose, lyocell, polylactic acid, metal or blends thereof.
 8. The component of claim 1 in the form of a tire carcass, sidewall, belt, overlay, breaker, chipper, flipper or subtread.
 9. The component of claim 2, wherein the yarn is penetrated by a surface coating such that the coating comprises from 1 to 20 weight percent of the yarn plus coating.
 10. The component of claim 6, wherein the core material is inorganic.
 11. The component of claim 7, wherein the aromatic polyamide is para-aramid.
 12. The component of claim 8, wherein the yarn is penetrated by a surface coating such that the coating comprises from 2 to 15 weight percent of the yarn plus coating.
 13. A method of reducing tire noise in a vehicle by providing a component in a tire comprising spun staple yarn having a linear density corresponding to a cotton count of from 17/1 to 10/5. 